Significance It is hypothesized that the recovery of function after cortical lesions is the result ofthe changes in the way the spared cerebral cortex encodes information that was formerly processed by the now-dead cortical tissue. It is further hypothesized that these same mechanisms that occur following peripheral damage and cortical lesions also occur as an individual improves their performance at a perceptual task with training. Objectives In this study, monkeys are trained to perform one of two auditory discrimination tasks. In both tasks the stimuli are essentially identical, except in one the monkey must detect a change in the order that four tone pips are presented in, and in the other the monkey must detect a change in the location of the same four tone pips. While the monkey performs this task, the activity of single neurons is recorded in the auditory cortex to determine if there are sub populations of neurons that selectively respond to the order of the four stimuli, or the location of the four stimuli. Small lesions of the cerebral cortex should then differentially effect the performance of the monkey on one, but not the other task. Results To date one monkey has been partially trained at a simplified version of this task. Future Directions This monkey will be the first to provide the necessary behavioral and neuronal data to address these question, and will likely be completed at the end of the next calendar year. KEYWORDS sound localization, primary auditory cortex, population response, temproal order processing